The present invention relates to the field of fluid mixing valve assemblies. More particularly, the invention concerns thermostatically controlled mixing valve assemblies in which a thermostat is immersed in the fluid flowing through the valve.
Thermostatic control valve assemblies are well known in the art and have long been utilized in various applications including group showers, washing stations, hospital hydrotherapy installations and in many industrial applications where precision thermostatic water blending is essential. In order to operate properly, the hot and cold water entering such a valve assembly must be thoroughly blended before the temperature of the mixture is sensed by the thermostat. If the hot and cold water are not adequately mixed, the valve assembly can behave erratically because the temperature sensor sees pockets of hot and cold water instead of a mixture that is at a single temperature throughout. One problem that has long persisted in the art is the inability of most valve assemblies to adequately mix the hot and cold water over a wide range of flow rates. Consequently, multiple valves often have to be used to satisfy flow requirements.
Another problem that has persisted in the art is the physical size of the valve assembly required for a specific application. Often, the valve assembly is simply too large because of the need for a large mixing chamber to adequately mix the hot and cold water. What is needed is a thermostatic control valve assembly having an improved mixing chamber that has the ability to thoroughly mix the hot and cold water over a wide range of flow rates, and which does so in a smaller physical space than valve assemblies currently known in the art.
Still another problem of previously known thermostatic mixing valves is the performance of the mixing valve at low flow conditions. Because inadequate mixing occurs at low flow conditions, the performance of the valve becomes erratic due to the resulting temperature fluctuations. Locating the thermostat further downstream of the valve inlets and mixing ports improves mixing to reduce the erratic tendencies of the valve. However, because the fluid must travel further to reach the thermostat, the response time of the valve increases. Therefore, an improved thermostatic mixing valve is needed which promotes mixing at low flow conditions to reduce erratic tendencies of the valve while still responding quickly to fluid temperature changes.